SAW filters can be used in high-frequency circuits, e.g., in a bandpass filter. A SAW filter comprises a piezoelectric material and an electrode structure. The electrodes can transform a high-frequency signal into an acoustic wave which propagates along the surface of the piezoelectric material. Further, a second electrode structure is arranged to transform the acoustic wave back into a high-frequency signal thereby selectively extracting a desired frequency band.
SAW filters can be used as part of a front-end module of a mobile phone. There is a need to reduce the overall cost and to simplify the design. Accordingly, SAW filters without a matching network are requested.
U.S. Pat. No. 5,729,186 discloses a SAW filter that comprises thin aluminum electrodes on a lithium niobate substrate with a cut angle of 41°. This filter achieves a relative bandwidth of 9%. Further, SAW filters comprising a lithium niobate substrate with cut angles of 64° are known. These filters have a lower loss than the filters disclosed by U.S. Pat. No. 5,729,186 but with the drawback of a smaller achievable bandwidth.